       Re: Handling expressions. Could any one find a more direct way?

• To: mathgroup at smc.vnet.net
• Subject: [mg39921] Re: Handling expressions. Could any one find a more direct way?
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Wed, 12 Mar 2003 02:28:00 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <b4k3og\$8fl\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

Solve[0 == # & /@ CoefficientList[Numerator[Together[A - b]], s],
{k10, k21, k12, k13, k31}]

Regards
Jens

Guillermo Sanchez wrote:
>
> (*A need to obtain   {k10, k21, k12, k13, k31}  knowing that A = b
> where*)
>
> A = 0.1/(0.1 + s) + 0.2/(1 + s) + 0.7/(5 + s);
>
> b = (k21*k31 + k21*s + k31*s + s^2)/(k10*k21*k31 + k10*k21*s +
> k13*k21*s +
>      k10*k31*s + k12*k31*s + k21*k31*s + k10*s^2 + k12*s^2 + k13*s^2 +
>      k21*s^2 + k31*s^2 + s^3);
>
> (*Here is my procedure*)
>
> A1 = Together[ExpandAll[Factor[A]]]
>
> n1 = Numerator[A1]
>
> d1 = Denominator[A1]
>
> n2 = Collect[Numerator[b], s]
>
> d2 = Collect[Denominator[b], s]
>
> (*Now, handing the solution for previous output -they are been
> eliminated in this mail- I can obtain  {k10, k21, k12, k13, k31}*)
>
> Solve[{k21*k31== 0.67, 2.39 == k21 + k31, k10*k21*k31 == 0.5,
>    k10*k21 + k13*k21 + k10*k31 + k12*k31 + k21*k31 == 5.6,
>    k10 + k12 + k13 + k21 + k31 == 6.1}, {k10, k21, k12, k13, k31}]
>
>   (* Could any one find a more direct way?*)
>
>   Guillermo Sanchez

```

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